Reasoning runs on a fast automatic system and a slow deliberate one, and most documented biases are the first operating unchecked.
Popularised by Kahneman in 2011. The strict two-system division is now contested in favour of a continuum of automaticity, but the distinction survives as a framework for why deliberate checking works at all.
In practice
- A driver brakes before consciously seeing the child, and then spends the evening reasoning about whether the road was safe.
- An interviewer forms a view in ninety seconds and produces a page of justification afterwards, sincerely.
- Possible explanations
- The explanation is capacity: fast associative processing is cheap and always running, and deliberate checking is expensive, so it is deployed selectively.
- In its favour
- It predicts what is observed: time pressure and cognitive load increase biased answers, and prompting deliberate checking reduces some of them.
- Against it
- The strict division into two systems is contested in favour of a continuum of automaticity, the labels describe rather than explain, and several biases persist under careful deliberation.
- Standing
- Popularised by Kahneman. The strict two-system division is now contested in favour of a continuum of automaticity.
- Subject
- Decision-making & Reasoning
- Essay
- Why reasoning works the way it does